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首页> 外文期刊>Combustion Science and Technology >Effects of Water Vapor Addition on the Flame Structure and Soot Formation in a Laminar Ethanol/air Coflow Flame
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Effects of Water Vapor Addition on the Flame Structure and Soot Formation in a Laminar Ethanol/air Coflow Flame

机译：水蒸气添加对层状乙醇/空气COFLOW火焰中的火焰结构和烟尘形成的影响

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Ethanol is a promising alternative fuel to gasoline engines; however, the problem of particulate matter (PM) emissions still exists when ethanol is applied to gasoline direct injection (GDI) engines, especially under high load. Water injection is proved to be an effective way to reduce the PM emissions and engine knocking, simultaneously. In this work, a numerical calculation was carried out in an ethanol/air coflow diffusion flame to investigate the effects of water vapor addition on the flame structure and soot formation. A complete step-by-step decoupling method was proposed to numerically isolate the dilution, density, transport, thermal, radiative and chemical effects of water vapor by introducing several virtual species. Results show that the temperature distribution of the flame is mainly affected by the dilution effect and thermal effect of water vapor, followed by radiative effect and chemical effect. The mole fraction of OH radical increases because of the enhancement of the reaction H2O + H OH + H-2 and O + H2O OH + OH, while the conversion of CO to CO2 is promoted through the reaction CO + OH CO2 + H, due to the chemical effect. Soot volume fraction is also reduced, where the dilution and chemical effects play the most important roles. Hydrogen-abstraction-carbon-addition (HACA) surface growth and OH oxidation are the processes controlling the soot mass addition and consumption, respectively. HACA rate is mainly affected by the dilution and chemical effects. However, chemical effect has little influence on the OH oxidation rate, since the collision probability of OH with soot particles remains almost unchanged as a result of the increase of OH concentration and the decrease of soot volume fraction under the chemical effect.
机译：乙醇是汽油发动机有前途的替代燃料;然而，当乙醇应用于汽油直接注射（GDI）发动机时，颗粒物质（PM）排放仍然存在于汽油直接注射（GDI）发动机。被证明是注水是一种有效的方法，可以同时减少PM排放和发动机敲击。在这项工作中，在乙醇/空气COFLOW扩散火焰中进行数值计算，以研究水蒸气对火焰结构和烟灰形成的影响。提出了一种完整的逐步去耦方法，以通过引入若干虚拟物种来以数字分离水蒸气的稀释度，密度，运输，热，辐射和化学效果。结果表明，火焰的温度分布主要受水蒸汽的稀释效果和热效应的影响，其次是辐射效应和化学效果。由于反应H 2 O + H OH + H-2和O + H 2 O OH + OH的增强，OH基团的摩尔分数增加，而CO至CO 2的转化通过反应CO + OH CO2 + H促进，因此化学效果。烟灰体积分数也降低，其中稀释和化学效果发挥着最重要的作用。氢气抽取 - 碳添加（HACA）表面生长和OH氧化分别是控制烟灰大气添加和消耗的过程。 Haca率主要受稀释和化学效果的影响。然而，化学效果对OH氧化速率影响不大，因为OH与烟灰颗粒的碰撞概率仍然不变，导致OH浓度的增加和烟灰体积分数下的化学效果降低。

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